Zinc Recovery Process

The recovery of zinc can be done through various processes depending on the type of zinc ore and the impurities associated with it. Here, we will discuss the commonly used processes for zinc recovery:

Roasting and Leaching Process: This process is used for the recovery of zinc from sulfide ores like sphalerite (ZnS). The ore is roasted in the presence of air to convert the sulfide into oxide. The resulting zinc oxide is then leached with sulfuric acid to produce zinc sulfate solution. Zinc is then precipitated from the solution by adding zinc dust or by electrolysis.

Electrolysis Process: This process is used for the recovery of zinc from zinc sulfate solution obtained by leaching of zinc oxide ores. The solution is purified and then electrolyzed using lead anodes and aluminum cathodes. Zinc is deposited on the cathode while sulfuric acid is regenerated at the anode.

Waelz Process: This process is used for the recovery of zinc from zinc-containing waste materials like zinc ash, dross, and smelter flue dust. The waste materials are mixed with coal and heated in a Waelz kiln to produce zinc oxide and iron oxide. The zinc oxide is then leached with sulfuric acid and the resulting solution is treated by electrolysis to recover zinc.

Imperial Smelting Process (ISP): This process is used for the recovery of zinc from mixed sulfide and oxide ores like those found in the Red Dog Mine in Alaska. The ore is first roasted to convert the sulfide to oxide. The oxide is then smelted with coke and fluxes to produce a crude lead-zinc alloy. The lead is then separated from the zinc by fractional distillation.

Solvent Extraction and Electrowinning (SX-EW) Process: This process is used for the recovery of zinc from low-grade oxide ores. The ore is first leached with sulfuric acid to produce a zinc sulfate solution. The solution is then purified and treated with an organic solvent that selectively extracts the zinc ions. The zinc is then recovered from the organic solvent by electrowinning.

In conclusion, there are various processes available for the recovery of zinc depending on the type of zinc ore and the impurities present. These processes involve a combination of physical and chemical methods to extract and purify the zinc metal from the ore.